Enabling Asset Security & Management BPS.0707.01P Batteries and Power Supplies

Enabling Asset Security & ManagementBPS.0707.01P

Batteries and Power SuppliesBatteries and Power Supplies

2Enabling Asset Security & ManagementBPS.0707.01P

Powering Your ApplicationPowering Your Application

Can be a complex decision Many factors to be

considered Technical Commercial Operational Support

The success or failure of your application can be affected


Power SuppliesPower Supplies

Available sources of power AC source Batteries Vehicle switched or unswitched? Solar cell Standby requirements Multiple sources

Operating modes Differences between normal & standby

operation


GuidelinesGuidelines

Optimize for low power operation Exception based reporting Power GPS on demand

Geofencing & distance based scripts require the DMR to be constantly receiving GPS positions

Sleep modes Minimize receive periods to minimize power

consumption


Power ConsumptionPower Consumption

DMR-200 power consumption Receiving 0.8 W

Idle 0.25 W GPS 1.2 W Transmitting 10.2 W Heater (activated at -25°C) 2.8 W Sleep (@ 12 V) .005 W

I/O power consumption Displays, keyboards, etc. Sensors, actuators, etc.


Typical Power ConsumptionTypical Power Consumption

Normal Operation ~ 1 Watt (~2 Ah/day @ 12V)

GPS push to fix ~ 0.5 Watts (~1 Ah/day @ 12V)

Low Power (no listen) 1 hour reporting~ 0.1 Watts ( ~0.2 Ah/day @ 12V) 4 hour reporting~ 0.03 Watts ( ~0.05 Ah/day @ 12V) 8 hour reporting~ 0.02 Watts ( ~0.03 Ah/day @ 12V) 1 / day reporting ~ 0.01 Watts ( ~0.02 Ah/day @ 12V)

Low Power (10 minute listen) 1 hour reporting~ 0.2 Watts ( ~0.3 Ah/day @ 12V) 4 hour reporting~ 0.04 Watts ( ~0.1 Ah/day @ 12V) 8 hour reporting~ 0.03 Watts ( ~0.05 Ah/day @ 12V) 1 / day reporting ~ 0.01 Watts ( ~0.03 Ah/day @ 12V)


Calculating Power ConsumptionCalculating Power Consumption

Determine sequences of operation for the DMR-200 terminal # of terminal originated messages a day? When can terminal receive a message? How long will terminal be in sleep mode? Will terminal be in -25°C environment? Will digital open collector output be used?

Calculate power consumption for operating period


ExampleExample

Transmit 1 message per day Listen for 10 minutes after each

transmission Shutdown the rest of the time Sequences

Acquire bulletin board Acquire GPS Acquire traffic channel Monitor bulletin board Transmit Listen for 5 frames Sleep


Power Calculation – 1 Tx Per DayPower Calculation – 1 Tx Per Day

Time (seconds) Power (Watts) Energy (Joules)

Acquire bulletin board 140 0.9 126

Acquire GPS 60 0.5 30

Acquire traffic channel 24 0.9 22

Monitor bulletin board 60 0.9 54

Transmit 8 10 80

Listen for 5 frames 120 0.9 108

Idle 530 0.25 133

Sleep 85458 0.006 513

Total 86400 0.012 1065

Average current @ 12V (Amps) 0.001

Amp hours per day 0.025


Power Calculation – 2 Tx Per DayPower Calculation – 2 Tx Per Day

Time (seconds) Power (Watts) Energy (Joules)

Acquire bulletin board 140 0.9 126

Acquire GPS 60 0.5 30

Acquire traffic channel 24 0.9 22

Monitor bulletin board 60 0.9 54

Transmit 8 10 80

Listen for 5 frames 120 0.9 108

Idle 530 0.25 133

Additional transmit cycle 942 0.586 552

Sleep 84516 0.006 507

Total 86400 0.019 1611

Average current @ 12V (Amps) 0.002

Amp hours per day 0.037


Battery Technology SelectionBattery Technology Selection

Primary - non rechargeable Secondary - rechargeable Considerations

Service life Operating mode Frequency of reporting Operating environment

Temperature range Available power sources

Charge requirements


Primary Batteries - Primary Batteries - Non rechargeableNon rechargeable

Carbon Zinc Low power density & short shelf life D cell – 8Ah @ 1.5V Lowest cost

Alkaline Moderate power density & 5 year shelf life D cell – 18 Ah @ 1.5V Moderate cost

Lithium Thionyl Chloride High power density & 10 year shelf life D cell – 13 Ah @ 3.6V Highest cost Must use high rate versions for peak tx currents


Secondary Batteries - Secondary Batteries - RechargeableRechargeable

Lithium-ion (Li-ion) Highest power density Highest cost Stringent charging requirements Good self-discharge rate Small form factor Limited peak current capability

Sealed Lead Acid (SLA) Most popular – well understood Good cost performance trade-

off Easier to recharge Lowest power density Lowest self-discharge rate Heavy

Nickel Metal Hydride (NiMH) Middle of the road Highest self-discharge rate

Nickel Cadmium (NiCd) High current applications High self-discharge rate Memory effects if not managed

correctly


Solar CellsSolar Cells

Ensure adequate output to recharge batteries under all conditions. Cloudy days Short winter days Accumulation of dirt/snow/debris Orientation to the sun

Ensure battery capacity to cover long nights and cloudy days

Charge controller generally required Relatively expensive & fragile


Things To WatchThings To Watch

Effects of temperature Many batteries lose capacity @ high or low

temperatures Minimum battery voltage at end of life

Ah ratings usually specify a minimum voltagePeak current

Many technologies typically cannot deliver the peak current required during transmit

Out gassing Batteries inside a sealed enclosure can explode

Accidental discharge A lot of energy in a very small package Product liability issues


Specification Checklist - 1Specification Checklist - 1

Voltage It is important to know not only the nominal voltage, but also the

minimum and maximum for the application. As an example, a 7.2 volt nominal nickel metal hydride pack will vary from 6.0 volts in a fully discharged state to 9.6 volts at the end of charge.

Discharge Current Both the average and maximum discharge currents are needed to

specify the proper battery. Most often, the average current determines how large the battery must be to operate the device for a given amount of time. But in some cases there are intermittent high loads, and the maximum current requires a larger battery for the device to operate at all.

Cycle Life If the battery is rechargeable, the number of charges and

discharges required over the life of the battery will help determine the ideal chemistry and capacity.



Service Life For a non-rechargeable or a backup battery, the size and chemistry

will be determined by the required life, as well as the discharge and temperature profiles.

Cost A technically ideal battery could be cost prohibitive. Note, however,

that a more expensive battery can sometimes pay for itself several times over in the form of reduced replacement costs and/or better performance.

One-Time-Use or Rechargeable One-time-use or primary cells, once discarded must be replaced

with a fresh battery. Rechargeable or secondary cells can be used many times, but require a charger.

Charging Improper charging is the leading cause of early failure in

rechargeable batteries. A better charger will often pay for itself in increased performance and reduced replacement costs.



Weight & Dimension Cells of various chemistries are made in a wide variety of sizes,

and custom battery packs offer even more flexibility. Note that a smaller, lighter battery with the same energy usually costs more than a larger, heavier one, and even if money is no object, there is a limit to how small and light a battery can be.

Temperature If your product will be used or stored in hot or cold conditions,

battery performance and life could be affected. Low temperatures compromise performance, while high temperatures dramatically reduce the life of cells.

Storage Duration - Consider not only inventory turnover, but how long the

batteries will spend in the supply chain and in your customer's inventory before being used or recharged.

Conditions - What temperature and moisture conditions will your battery be stored under?



Self Discharge This is a measure of how quickly a cell will lose its energy

while sitting on the shelf. Note that higher temperatures will significantly reduce the shelf life of any battery.

Primary Batteries: Carbon 2.5 years Alkaline 5 years Lithium 10+ years

Rechargeable batteries: Lead acid 6 months between "top off charges“ NiCds 1 year between charges NiMH 1 year between charges Lithium 1 year between charges

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Enabling Asset Security & Management BPS.0707.01P Batteries and Power Supplies